Digital broadcasting may have a quality superior to analog broadcasting. However, digital broadcasting may not be received when a channel is degraded below a particular standard, while a receiving quality of analog broadcasting deteriorates as a channel is degraded. To overcome the disadvantage, a layered modulation may be applied.
Also, a digital wireless communication system has been developed after the advent of a second generation mobile communication system such as a Global System for Mobile Communication (GSM) scheme and a Code Division Multiple Access (CDMA) scheme. Currently, a convergence technology that provides a wireless multicast/broadcast service through a separate multicast/broadcast channel comes into the spotlight in a wireless communication system. Currently, a technology that provides a particular terminal with a Video On Demand (VOD) service or a multimedia service including a video through a given unicast channel is also the focus of attention.
Scalable Video Coding (SVC), which is a multimedia compression technology for source coding required in a broadcasting or communication system, is also in the limelight since it may satisfy a variety of requirements and Quality of Service (QoS). SVC is a source coding scheme appropriate for a heterogeneous network where a broadcasting network and other communication networks are connected, and may transmit a single video source using a plurality of layers. A receiving end may receive a portion of or entire layers with a higher priority depending on conditions such as a channel state, and replay a video with variable qualities. Layering of SVC may include a temporal layering, a spatial layering, and a quality layering. The temporal layering may variably control the number of frames per second, the spatial layering may variably control a size of a replay screen, and the quality layering may variably control a video quality such as the number of bits per pixel. Also, in SVC, each layer may not be independently decoded. That is, only when layers with higher priority than a corresponding layer itself are decoded may the corresponding layer be decoded, which is known as layered decoding.
In a wireless broadcasting and communication system, a transmission scheme that has a number of layers is required to make the most use of SVC.
As an example of a wireless transmission technology supporting layer transmission of a multimedia source in a conventional art, mediaFLO of Qualcomm® has proposed layered modulation. Layered modulation may first modulate multimedia data of a basic layer using a Quadrature Phase-shift keying (QPSK), and include an enhanced layer to the multimedia data of the basic layer, and transmit data of the two layers using 16-state Quadrature Amplitude Modulation (16-QAM). In this instance, a terminal with a suitable channel state may receive the two layers without error, and a terminal with an unsuitable channel state may receive only data of the basic layer. Although layered modulation may be easily embodied due to the simple structure, the number of layers may be limited.
Accordingly, a wireless transmission technology that may have a number of layers is required.